Refrigerant compressors

ABSTRACT

A refrigerant compressor includes a cylinder block, a front housing, and a sealing member. The cylinder block has a cylindrical portion. The cylindrical portion has an internal thread formed on an end thereof. The front housing having an external thread engages the internal thread. The front housing is fixed to the cylinder block and forms a crank chamber with the cylinder block. The pressure capacity of the refrigerant compressor may be increased without an increase in the size of the compressor.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to refrigerant compressors, and more particularly, to piston-type compressors having a cylinder block, a front housing, and a crank chamber, which is formed by the cylinder block and the front housing.

[0003] 2. Description of Related Art

[0004] Refrigerant compressors having a cylinder block and a front housing are known in the art. In the known compressor, the front housing is fixed to the cylinder block and forms a crank chamber with the cylinder block. The front housing and the cylinder block are fixed securely together by a plurality of bolts. The plurality of bolts may penetrate a flange portion formed on an outer surface of the front housing and a plurality of bosses for receiving the plurality of bolts formed on an outer circumference of cylinder block. The plurality of bolts also may penetrate the front housing and the cylinder block through the crank chamber, and may penetrate a cylinder head forming a suction chamber and a discharge chamber with the cylinder block. Thus, the front housing is fixed securely to the cylinder block by the plurality of bolts.

[0005] Recently, air-conditioning systems using carbon dioxide (CO₂) as refrigerant have been developed in order to help prevent global warming. The saturated vapor pressure of carbon dioxide at an ambient temperature is higher than that of hydrofluorocarbon, e.g., HFC-134a, which has been used as refrigerant for air-conditioning systems. For example, when the ambient temperature is at about 25° C. (about 77° F.), the saturated vapor pressure of carbon dioxide is at about 6.4 MPa (about 66 kgf/cm²), and that of hydrofluorocarbon is at about 0.7 MPa (about 7 kgf/cm²). Therefore, a compressor for use in air-conditioning systems using carbon dioxide as refrigerant must have a structure for enduring elevated pressures. An increase of a bolt diameter is required to increase the pressure capacity in the known compressor having the front housing and the cylinder block, both of which are fixed by the plurality of bolts or a plurality of through-bolts. When the bolt diameter is increased, a diameter of the front housing and the cylinder block may be also increased. As a result, problems associated with an increase of the size of the compressor may occur.

SUMMARY OF THE INVENTION

[0006] A need has arisen to provide refrigerant compressors having increased pressure capacity without increasing the size of the compressors.

[0007] In an embodiment of this invention, a refrigerant compressor comprises a cylinder block and a front housing. The cylinder block has a cylindrical portion. The cylindrical portion has an internal thread formed on an end thereof. The front housing having an external thread is engaged by the internal thread of the cylindrical portion. The front housing is fixed to the cylinder block and forms a crank chamber with the cylinder block.

[0008] In another embodiment of this invention, a refrigerant compressor comprises a cylinder block and a front housing. The cylinder block has a cylindrical portion. The cylindrical portion has an external thread formed on an end thereof. The front housing having an internal thread is engaged by the external thread of the cylindrical portion. The front housing is fixed to the cylinder block and forms a crank chamber with the cylinder block.

[0009] Objects, features, and advantages of embodiments of this invention will be apparent to persons of ordinary skill in the art from the following detailed description of the invention and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present invention may be more readily understood with reference to the following drawings.

[0011]FIG. 1a is a longitudinal, cross-sectional view of a refrigerant compressor, according to an embodiment of the present invention.

[0012]FIG. 1b is a partially cut-away, axial view taken along the line B-B of FIG. 1a.

[0013]FIG. 2a is an enlarged, first detailed partial view of an alternative joint portion of a front housing and a cylinder block depicted in FIG. 1a.

[0014]FIG. 2b is an enlarged, second detailed partial view of an alternative joint portion of a front housing and a cylinder block depicted in FIG. 1a.

[0015]FIG. 3 is an enlarged, detailed partial view, which corresponds to FIG. 2a, according to an alternative embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0016] Referring to FIGS. 1a-2 b, an embodiment of a refrigerant compressor according to the present invention is shown. As shown in FIGS. 1a and 1 b, a refrigerant compressor 100 comprises a cylinder block 1, a front housing 6, and a cylinder head 13. Cylinder block 1 has a cylindrical portion 1 a. An internal thread 1 b is formed on an end of an inner surface of cylindrical portion 1 a. Cylinder head 13 is fixed to cylinder block 1 by the plurality of bolts 12. A plurality of cylinder bores 1 c are formed in cylinder block 1 and are arranged radially with respect to the central axis of cylinder block 1. One of pistons 2 is accommodated in each of cylinder bores 1 c, and pistons 2 are independently and reciprocally movable therein between a top dead center and a bottom dead center. A drive shaft 3 and a swash plate 4 are disposed in cylinder block 1. Swash plate 4 is mounted on a drive shaft 3 via a known link mechanism. Hemispherical shoes 5 a and 5 b are disposed between each sliding surface of swash plate 4 and inner surfaces of piston skirt portions of pistons 2, so that pistons 2 may slide along the side surface of swash plate 4. Thus, piston 2 is connected to swash plate 4 with shoes 5 a and 5 b. A plurality of mounting bosses Id for use in attaching the compressor at suitable positions in a vehicle are formed on an outer surface of cylinder block 1.

[0017] An external thread 6 a is formed on an end of a peripheral surface of front housing 6 and fixedly engages internal thread 1 b of cylinder block 1. A crank chamber 7 is formed in cooperation with cylinder block 1 and front housing 6. Drive shaft 3 passes through a central axis of front housing 6. A sealing member 8 surrounding drive shaft 3 is disposed in front housing 6. A plurality of radial lubrication passages 6 b communicate between crank chamber 7 and sealing member 8. An electromagnetic clutch 9, which is rotatably supported by and mounted on front housing 6, is connected to drive shaft 3. A drive belt (not shown) is provided to transfer motion between electromagnetic clutch 9 and a crankshaft of an engine of a vehicle (not shown).

[0018] As shown in FIG. 2a, an O-ring 10 is disposed between connecting portions of cylinder block 1 and front housing 6 for sealing thereof. A joint portion 11 is formed around an end of front housing 6 and projects in an axial direction to define an axial line between cylinder block 1 and front housing 6. A projecting portion 6 c is formed on a peripheral portion of front housing 6 to prevent connecting portions of cylinder block 1 and front housing 6 from loosen. Projecting portion 6 c may be a single portion or one of a plurality of such portions. Alternatively, as shown in FIG. 2b, a projecting portion 1 e is formed on a cylinder block 1 to prevent connecting portions of cylinder block 1 and front housing 6 from loosening. Projecting portion 1 e may be a single portion or one of a plurality of such portions.

[0019] Referring again to FIGS. 1a and 1 b, compressor 100 has cylinder head 13, which is fixed to cylinder block 1 by a plurality of bolts 12. A suction chamber 13 a and a discharge chamber 13 b is formed by the cooperation of cylinder block 1 and cylinder head. A mounting boss 13 c for use in attaching the compressor at suitable position in the vehicle is formed on an outer surface of cylinder head 13.

[0020] In operation, when a driving force is transferred from an external driving force an engine of a vehicle) via a belt and electromagnetic clutch 9, drive shaft 3 is rotated. Electromagnetic clutch 9 transmits a rotating force to drive shaft 3, or disconnects a rotating force from drive shaft 3. The rotation of drive shaft 3 is transferred to swash plate 4 via a known linkage mechanism, so that, with respect to the rotation of drive shaft 4, the inclined surface of swash plate 4 moves axially right and left. Consequently, pistons 2, which are operatively connected to swash plate 4 by means of shoes 5 a and 5 b, reciprocate within cylinder bores 1 c. As pistons 2 reciprocate, refrigerant gas, which is introduced into suction chamber 13 a from a fluid inlet port (not shown), is drawn into each cylinder bore 1 c and is compressed. The compressed refrigerant gas is discharged into discharge chamber 13 b from each cylinder bores 1 c and therefrom into a fluid circuit, for example, a cooling circuit, through a fluid outlet port (not shown).

[0021] In compressor 100, front housing 6 and cylinder block 1 are joined by engaging external thread 6 a of front housing 6 with internal thread 1 b of cylinder block 1. The joint portion between external thread 6 a and internal thread 1 b is sealed by O-ring 10. The strength of the joint portion between front housing 6 and cylinder block 1 may be increased by adjusting a height of the thread, a pitch of the thread, the number of threads of external thread 6 a and internal thread 1 b, or combination thereof. Therefore, the pressure capacity of compressor 100 may be greater than that of a known refrigerant compressor. Because the bolts are no longer necessary to connect front housing 6 to cylinder block 1, if the pressure capacity of compressor 100 is increased, the size of compressor 100 may not be increased. Therefore, an increase of the pressure capacity of compressor 100 may be achieved without an increase of the size of the compressor.

[0022] Because compressor 100 has projecting portion 1 e or projecting portion 6 c, the joint portion between front housing 6 and cylinder block 1 may not work loose. Moreover, because swash-plate type compressor 100 has joint portion 11, when front housing 6 engages cylinder block 1, the axial line of cylinder block 1 may define an axial line of front housing 6. Moreover, because compressor 100 has the plurality of lubrication passages 6 b communicating between sealing member 8 and crank chamber 7, lubricating oil may be provided to sealing member 8 from crank chamber 7, regardless of the relative rotational position of front housing 6 against cylinder block 1 after front housing 6 is connected to cylinder block 1. Moreover, cylinder head 13 is fixed to cylinder block 1 by the plurality of bolts 12. When front housing 6 is fixed to cylinder block 1, the relative position between the plurality of mounting bosses 1 d formed on the outer surface of cylinder block 1 and mounting boss 13 c formed on the outer surface of cylinder head 13 may not be disturbed. Therefore, the plurality of mounting bosses 1 d and mounting boss 13 c may be smoothly attached at predetermined positions to structural parts of the vehicle, in other words, compressor 100 may be smoothly attached at predetermined positions to structural parts of the vehicle.

[0023] Referring to FIG. 3, in an alternative embodiment of the present invention, a small screw 14 pressedly fitted into cylinder block 1 through front housing 6 may be used as a loosening stopper for the joint portion between cylinder block 1 and front housing 6. Alternatively, an internal thread formed on front housing 6 may engage an external thread formed on an end of cylindrical portion 1 a of cylinder block 1, and front housing 6 may be fixed thereby to cylinder block 1. Moreover, in another alternative embodiment of the present invention, an engaged portion between cylinder block 1 and front housing 4 may be sealed by using a sealing member, e.g., a gasket; a coating material sprayed or coated on the internal or external thread of cylinder block 1 or front housing 6; a coating material as sort of a tape, which is wrapped around the joint portion, or the like, is within the contemplation of the present invention. Moreover, if the manufacturing tolerances between the external thread and the internal thread of cylinder block 1 or front housing 6 are increased and both the external and internal threads engage at a high surface pressure, the joint portion between cylinder block 1 and front housing 6 may be sealed without disposing a sealing member between cylinder block 1 and front housing 6.

[0024] As described above, in a refrigerant compressor with respect to embodiments of the present invention, a front housing is fixed to a cylinder block, in that an internal thread formed on the front housing engages an external thread formed on the cylinder block, or an external thread formed on the front housing engages an internal thread formed on the cylinder block. The strength of the joint portion between the front housing and the cylinder block may be increased by adjusting a height of the thread, a pitch of the thread, the number of threads of the external thread and the internal thread, and combinations thereof. Therefore, the pressure capacity of the refrigerant compressor may be greater than that of a known refrigerant compressor. Moreover, because the bolts are no longer necessary to fix the front housing to the cylinder block, if the pressure capacity of the refrigerant compressor is increased, the size of the refrigerant compressor may remain the same. Therefore, an increase of the pressure capacity of the refrigerant compressor may be achieved without an increase of the size of the compressor. Moreover, the embodiments of the present invention are applied to the swash plate piston-type compressors, however, the present invention may be applied to any compressors or fluid displacement apparatus.

[0025] Although the present invention has been described in connection with preferred embodiments, the invention is not limited thereto. It will be understood by those skilled in the art that variations and modifications may be made within the scope and spirit of this invention, as defined by the following claims. 

What is claimed is:
 1. A refrigerant compressor comprising: a cylinder block having a cylindrical portion, said cylindrical portion has an internal thread formed on an end thereof; and a front housing having an external thread engaged by said internal thread, and said front housing fixed to said cylinder block and forming a crank chamber with said cylinder block.
 2. The refrigerant compressor of claim 1, further comprising: a sealing member sealing a joint portion between said front housing and said cylinder block.
 3. The refrigerant compressor of claim 1, wherein a projecting portion is formed on an end of said cylinder block.
 4. The refrigerant compressor of claim 1, wherein a projecting portion is formed on an end of a peripheral portion of said front housing.
 5. The refrigerant compressor of claim 1, wherein a screw is pressedly fitted into an end surface of said cylinder block through said front housing.
 6. The refrigerant compressor of claim 1, wherein a joint portion is formed around an end of said front housing defines an axial line between said cylinder block and said front housing.
 7. The refrigerant compressor of claim 1, wherein a plurality of radial lubrication passages communicate between said crank chamber and said sealing member.
 8. The refrigerant compressor of claim 1, further comprising: a cylinder head fixed to said cylinder block at an opposite side of said front housing by a plurality of bolts, said cylinder block forming a suction chamber and discharge chamber with said cylinder block; and a plurality of mounting bosses for attaching to a vehicle formed on an outer surface of said cylinder block and said cylinder head.
 9. The refrigerant compressor of claim 1, wherein said refrigerant compressor is a piston-type compressor.
 10. A refrigerant compressor comprising: a cylinder block having a cylindrical portion, said cylindrical portion has an external thread formed on an end thereof; and a front housing having an internal thread which engages said internal thread, and said front housing fixed to said cylinder block and forming a crank chamber with said cylinder block.
 11. The refrigerant compressor of claim 10, further comprising: a sealing member sealing a joint portion between said front housing and said cylinder block.
 12. The refrigerant compressor of claim 10, wherein a projecting portion is formed on an end of said cylinder block.
 13. The refrigerant compressor of claim 10, wherein a projecting portion is formed on an end of a peripheral portion of said front housing.
 14. The refrigerant compressor of claim 10, wherein a screw is pressedly fitted into an end surface of said cylinder block through said front housing.
 15. The refrigerant compressor of claim 10, wherein a joint portion is formed around an end of said front housing defines an axial line between said cylinder block and said front housing.
 16. The refrigerant compressor of claim 10, wherein a plurality of radial lubrication passages communicate between said crank chamber and said sealing member.
 17. The refrigerant compressor of claim 10, further comprising: a cylinder head fixed to said cylinder block at an opposite side of said front housing by a plurality of bolts, said cylinder head forming a suction chamber and discharge chamber with said cylinder block; and a plurality of mounting bosses for attaching to a vehicle formed on an outer surface of said cylinder block and said cylinder head.
 18. The refrigerant compressor of claim 10, wherein said refrigerant compressor is a piston-type compressor. 